1. Field of the Invention
The present invention relates to a substrate processing method and a substrate processing apparatus applied to remove a resist from the surface of a substrate. The substrate includes a semiconductor wafer, a glass substrate for a liquid crystal display, a glass substrate for a plasma display, a glass substrate for an FED (Field Emission Display), an optical disc substrate, a magnetic disc substrate, a magneto-optical disc substrate, a photomask substrate, and so forth.
2. Description of Related Art
The manufacturing process of a semiconductor device includes, for example, a step of locally implanting impurities (ions), such as phosphorous, arsenic, and boron, on the surface of a semiconductor wafer (hereinafter, referred to simply as the wafer). In this step, in order to prevent ions from being implanted in an undesired portion, a resist made of a photosensitive resin is formed in a pattern on the surface of the wafer, so that a portion where the ion implantation is not desired is masked by the resist. The resist formed in a pattern on the surface of the wafer is unnecessary after the ion implantation. Resist removing processing is therefore performed after the ion implantation to remove the unnecessary resist on the surface of the wafer by stripping.
In the resist removing processing, the resist on the surface of the wafer is removed, for example, by ashing in an ashing apparatus. The wafer is then carried into a cleaning apparatus to remove resist polymer remaining after the ashing from the surface of the wafer.
In the ashing device, for example, the inside of a processing chamber accommodating the wafer is brought into an oxygen gas atmosphere and a microwave is irradiated into the oxygen gas atmosphere. This gives rise to a plasma of the oxygen gas (oxygen plasma) within the processing chamber, and this oxygen plasma is irradiated on the surface of the wafer. The resist film on the surface of the wafer is consequently removed by decomposition.
In the cleaning apparatus, for example, a chemical, such as APM (Ammonia-hydrogen Peroxide Mixture), is supplied to the surface of the wafer to apply cleaning processing (resist polymer removing processing) using the chemical to the surface of the wafer. The resist polymer adhering onto the surface of the wafer is removed by this cleaning processing.
Ashing using a plasma, however, has a problem that the surface of the wafer is damaged in a portion uncovered with the resist film (for example, an exposed oxide film).
Such being the case, as an alternative to the ashing by a plasma and the cleaning processing using a chemical, such as APM, it is proposed to supply SPM (Sulfuric acid/hydrogen Peroxide Mixture), which is a mixed liquid of sulfuric acid and a hydrogen peroxide liquid, to the surface of the wafer, so that the resist formed on the surface of the wafer is removed by stripping with a strong oxidation force of peroxomonosuliric acid (H2SO5) contained in the SPM.
However, because the surface of the resist has been altered (hardened) in an ion-implanted wafer (in particular, in the case of a high-dose ion implantation), the resist cannot be removed in a satisfactory manner or it takes time to remove the resist.